The invention relates generally to a method and apparatus for the serial comparison of electrocardiograms (ECGs), and more specifically to a method and apparatus for the serial comparison of ECGs using an ECG acquisition device.
When a patient is suffering from severe chest pain, clinicians must detect acute coronary syndromes, such as acute myocardial infarction and acute cardiac ischemia, quickly and accurately in order to prevent the death of cardiac muscle and, ultimately, the death of the patient. The ECG is critical for evaluating severe chest pain in a patient in order to detect and manage acute coronary syndromes.
When a patient suffering from severe chest pain is admitted into an emergency room, a single, initial ECG is immediately taken and analyzed by an emergency room clinician or by a computerized ECG interpretation program. Similarly, when emergency medical technicians arrive to care for a patient suffering from severe chest pain, a single, initial ECG is immediately taken and analyzed by the emergency medical technicians. Based on the analysis of these single, initial ECGs, acute myocardial infarction is only accurately detected one-half of the time and acute cardiac ischemia is only accurately detected one-third of the time. These poor detection rates are due to the fact that almost two-thirds of all ischemic episodes that occur in patient""s suffering from unstable coronary artery disease are silent and cannot be detected by the analysis of a single ECG. Also, fifteen to thirty percent of patients with unstable coronary disease have transient episodes of ST segment changes, predominately ST segment depression, that cannot be detected by the analysis of a single ECG. Similarly, acute coronary syndrome cannot be diagnosed based on a left bundle branch block appearing in a single ECG, because left bundle branch block is only associated with acute coronary syndrome if it is new, i.e., if the left bundle branch block has not occurred in the patient""s previous ECGs and then suddenly occurs in a subsequent ECG. However, it is desirable to detect new left bundle branch block, because new left bundle branch block is one of the strongest predictors of mortality in acute coronary syndrome patients.
The serial comparison of multiple ECGs can reveal acute coronary syndromes more accurately than the analysis of a single ECG. For example, if a clinician performs a serial comparison between an ECG acquired while the patient is in a stable cardiac period and a subsequent ECG indicating a left bundle branch block, the clinician can determine whether the left bundle branch block is new in order to predict acute myocardial infarction. If the serial comparison is performed by the clinician while the patient is suffering from severe chest pain, the clinician can detect and treat the myocardial infarction appropriately in a timely basis. Similarly, if a clinician performs a serial comparison while the patient is suffering from severe chest pain, the clinician can more accurately detect changes in the ST segment and changes in the amplitude of the T wave in order to predict acute cardiac ischemia and evolving acute myocardial infarction.
Even though the serial comparison of multiple ECGs can reveal acute coronary syndromes more accurately than the analysis of a single ECG, the existing ECG analysis programs used to perform serial comparisons have several limitations. ECG analysis programs for performing serial comparisons are generally implemented in ECG management systems, such as the GE Medical Systems Information Technologies, Inc. MUSE system, or in specially-designed ST segment monitoring devices, such as the GE Medical Systems Information Technologies, Inc. ST-Guard device. However, few emergency departments have access to ECG management systems or are equipped with specially-designed ST segment monitoring devices in order to perform serial comparisons quickly and accurately enough to detect acute coronary syndromes in patients suffering from severe chest pain. In the case of emergency medical technicians caring for a patient suffering from severe chest pain away from the hospital, a serial comparison cannot be performed between the patient""s ECGs stored in the ECG management system at the hospital and the ECGs acquired from the patient by the emergency medical technicians in time for the emergency medical technicians to detect and manage the patient""s acute coronary syndrome. Moreover, the serial comparison algorithms implemented in the ECG management systems are not designed specifically for detecting acute coronary syndromes, and thus, lack the sensitivity required to detect acute coronary syndromes in the most accurate manner.
In light of the limitations described above, a need exists for a method and apparatus for performing a serial comparison between a patient""s ECGs quickly and accurately in order to detect acute coronary syndrome in a patient suffering from severe chest pain, such as when a patient is admitted to an emergency room or when an emergency medical technician is treating a patient away from the hospital. Moreover, a need exists for a method and apparatus for ruling out acute coronary syndrome in order to discharge patients more quickly from the emergency room.
Accordingly, the invention provides a method and apparatus for acquiring ECGs from a patient with an ECG acquisition device and using the ECG acquisition device to perform a serial comparison between two or more of the ECGs acquired from the patient in order to accurately detect acute coronary syndromes.
The apparatus is an acquisition device for acquiring ECGs from a patient. The acquisition device includes an acquisition module for acquiring ECGs from the patient and a signal processor coupled to the acquisition module for performing a serial comparison between two or more of the ECGs acquired from the patient. The acquisition device may perform the serial comparison in real-time as ECGs are acquired from the patient in order to detect acute coronary syndrome. The acquisition device may be used to perform the serial comparison between the first ECG acquired from the patient during the cardiac episode, i.e., an index ECG, and subsequent ECGs. In addition, the acquisition device may be physically or wirelessly coupled to an ECG management system in order to access an ECG acquired from the patient during a stable cardiac period, i.e., a baseline ECG. If the acquisition device is wirelessly coupled to the ECG management system, the acquisition device may include a receiver for wirelessly communicating with an ECG management system located in a hospital remote from the acquisition device in order to access the patient""s baseline ECG stored in the ECG management system. The acquisition device is used to perform serial comparisons between the baseline ECG, the index ECG, and the subsequent ECGs.
For the method of the invention, ECGs are acquired from a patient with an ECG acquisition device and the ECG acquisition device is used to perform a serial comparison between two or more of the acquired ECGs. The serial comparison may be performed in real-time as ECGs are acquired from the patient in order to detect acute coronary syndrome. The serial comparison is performed between an index ECG and subsequent ECGs. The method may also include accessing a baseline ECG from an ECG management system coupled to the acquisition device or an ECG management system located in a hospital remote from the acquisition device. The serial comparisons may be performed between the baseline ECG, the index ECG, and the subsequent ECGs.
The invention also provides a method of performing a serial comparison between ECGs in order to accurately detect acute coronary syndrome. The method includes acquiring an index ECG and subsequent ECGs and identifying changes between the index ECG and the subsequent ECGs in QRS complex, ST elevation, ST depression, or T wave. The method also includes assigning severity values to the identified changes and analyzing the severity values according to a fuzzy logic algorithm. Acute myocardial infarction is indicated to a clinician if the severity value of the changes in the QRS complex is high, if the severity value of the changes in the ST elevation is high, if the severity value of the changes in the ST elevation and the ST depression are moderate, or if the severity value of the changes in the T wave inversion is equal to or greater than moderate. Acute ischemia is indicated to a clinician if the severity value of the changes in the ST depression is high, or if the severity level of the changes in the ST depression and the T wave inversion are moderate.
The invention further provides a software program for implementation in an ECG acquisition device and for performing a serial comparison between two or more ECGs acquired from a patient. The software program includes a management module for analyzing corresponding leads of the ECGs, for determining which corresponding leads indicate differences between the ECGs, for sorting the corresponding leads into groups according to the indicated differences, and for assigning a severity value to each one of the groups. The software program also includes a decision logic module for implementing a fuzzy logic algorithm to analyze the severity value assigned to each one of the groups and for outputting an indication of an acute coronary syndrome based on the analysis.
Various other features and advantages of the invention are set forth in the following drawings, detailed description and claims.